1. Field of the Invention
This invention relates to an improvement in the suspension apparatus for track-type vehicles, and more particularly to the suspension apparatus having track frames mounted on the main frame of the vehicle in a manner such as being freely oscillatory in a vertical plane.
2. Description of the Prior Art
As for the suspension apparatus of the kind specified, the diagonal brace type suspension apparatus has heretofore been commonly employed. However, the suspension apparatus of this type has been disadvantageous in that it is difficult to effect assembly and disassembly thereof because of its construction per se, in that the productivity in manufacturing track frames is limited, and in that it is inconvenient to convey the vehicles equipped with the suspension apparatus of this type by a wheeled vehicle, because the diagonal brace projects out.
As an example which has been devised to eliminate the above-mentioned disadvantages of the conventional diagonal brace type suspension apparatus, there has been suggested a system disclosed in the U.S. Pat. No. 3,980,149 which is arranged such that a pivot shaft transversely passes through a main frame of a track-type vehicle and extends there from on the left and right sides, that an equalizer bar is coupled with the left- and right-side track frames by means of spherical joints, and that "toe-in" which occurs during the oscillation thereof can be taken up by a deflection of the pivot shaft.
This construction is, however, disadvantageous in that the necessity of making the pivot shaft long enough so as to pass transversely through the main frame results in a substantial increase in the production cost thereof, and in that, because a deflection of the shaft takes place in the vertical direction, there is a tendency to cause partial wears of the track rollers and track links. Further, the construction of this type is disadvantageous in that, because there is almost no idly play in the ball joint portion between the track frames and the equalizer bar, a front portion of each of the track frames tends to be raised during the earth moving operation, which results in a considerable reduction in the tractive force of the vehicle due to the reduction in the area of the track frames kept in contact with the ground surface thereby causing a reduction in the operating performance of the vehicle as well as an accelerated wear of the track shoes.